I have an RK-3288 and I'm running into issues getting the correct display resolution over HDMI. It looks like i'm maybe getting 720 or lower, which is then upscaled in my monitor and looks horrible.
If I instead plug in VGA cable it looks good though.

I've tried forcing the HDMI to 1080p but I'm having issues. It looks like xrandr does not properly detect the HDMI port: